Dynamically adjusting an amount of log data generated for a storage system

ABSTRACT

Dynamically adjusting an amount of log data generated for a storage system that includes a plurality of storage devices, including: setting, for a component within the storage system, a logging level for the component, the logging level specifying the extent to which log data should be generated for a particular component; determining, in dependence upon one or more measured operating characteristics of the storage system, whether the logging level for the component should be changed; and responsive to determining that the logging level for the component should be changed, changing the logging level associated with the component.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 sets forth a block diagram of a storage system configured fordynamically adjusting an amount of log data generated according to someembodiments of the present disclosure.

FIG. 2 sets forth a block diagram of a storage array controller usefulin dynamically adjusting an amount of log data generated for a storagesystem according to some embodiments of the present disclosure.

FIG. 3 sets forth a block diagram illustrating a write buffer deviceuseful in storage systems configured for dynamically adjusting an amountof log data generated according to some embodiments of the presentdisclosure.

FIG. 4 illustrates a perspective view of a storage cluster with multiplestorage nodes and internal solid-state memory coupled to each storagenode to provide network attached storage or storage area network inaccordance with some embodiments of the present disclosure.

FIG. 5 illustrates a block diagram showing a communications interconnect(504) and power distribution bus coupling multiple storage nodesaccording to some embodiments of the present disclosure.

FIG. 6 is a multiple level block diagram, showing contents of a storagenode and contents of a non-volatile solid state storage of the storagenode according to some embodiments of the present disclosure.

FIG. 7 illustrates a storage server environment which may utilizeembodiments of the storage nodes and storage units according to someembodiments of the present disclosure.

FIG. 8 illustrates a blade hardware block diagram according to someembodiments of the present disclosure.

FIG. 9 sets forth a flow chart illustrating an example method ofdynamically adjusting an amount of log data generated for a storagesystem that includes a plurality of storage devices according to someembodiments of the present disclosure.

FIG. 10 sets forth a flow chart illustrating an additional examplemethod of dynamically adjusting an amount of log data generated for astorage system that includes a plurality of storage devices according tosome embodiments of the present disclosure.

FIG. 11 sets forth a flow chart illustrating an additional examplemethod of dynamically adjusting an amount of log data generated for astorage system that includes a plurality of storage devices according tosome embodiments of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Example methods, apparatus, and products for dynamically adjusting anamount of log data generated for a storage system in accordance with thepresent disclosure are described with reference to the accompanyingdrawings, beginning with FIG. 1. FIG. 1 sets forth a block diagram of astorage system (100) configured for dynamically adjusting an amount oflog data generated according to some embodiments of the presentdisclosure.

The storage system (100) depicted in FIG. 1 includes a plurality ofstorage arrays (102, 104), although dynamically adjusting an amount oflog data generated in accordance with embodiments of the presentdisclosure may be carried out in storage systems that include only asingle storage array. Each storage array (102, 104) may be embodied as acollection of computer hardware devices that provide persistent datastorage to users of the storage system (100). Each storage array (102,104) may include a collection of data storage devices that are mountedwithin one or more chassis, racks, or other enclosure. Although notexpressly depicted in FIG. 1, each storage array (102, 104) may includea plurality of power supplies that deliver power to one or morecomponents within the storage system (100) via a power bus, each storagearray (102, 104) may include a plurality of data communications networksthat enables one or more components within the storage system (100) tocommunicates, each storage array (102, 104) may include a plurality ofcooling components that are used to cool one or more components withinthe storage system (100), and so on.

The example storage arrays (102, 104) depicted in FIG. 1 may providepersistent data storage for computing devices (164, 166, 168, 170) thatare coupled to the storage system (100) via one or more datacommunications networks. Each of the computing devices (164, 166, 168,170) depicted in FIG. 1 may be embodied, for example, as a server, aworkstation, a personal computer, a notebook, a smartphone, a tabletcomputer, or the like. The computing devices (164, 166, 168, 170) in theexample of FIG. 1 are coupled for data communications to the storagearrays (102, 104) through a storage area network (‘SAN’) (158). The SAN(158) may be implemented with a variety of data communications fabrics,devices, and protocols. Example fabrics for such a SAN (158) may includeFibre Channel, Ethernet, Infiniband, Serial Attached Small ComputerSystem Interface (‘SAS’), and the like. Example data communicationsprotocols for use in such a SAN (158) may include Advanced TechnologyAttachment (‘ATA’), Fibre Channel Protocol, small computer systeminterface (‘SCSI’), iSCSI, HyperSCSI, and others. Readers willappreciate that a SAN is just one among many possible datacommunications couplings which may be implemented between a computingdevice (164, 166, 168, 170) and a storage array (102, 104). For example,the storage devices (146, 150) within the storage arrays (102, 104) mayalso be coupled to the computing devices (164, 166, 168, 170) as networkattached storage (‘NAS’) capable of facilitating file-level access, oreven using a SAN-NAS hybrid that offers both file-level protocols andblock-level protocols from the same system. Any other such datacommunications coupling is well within the scope of embodiments of thepresent disclosure.

The computing devices (164, 166, 168, 170) depicted in FIG. 1 are alsocoupled for data communications to the storage arrays (102, 104) througha local area network (160) (‘LAN’). The LAN (160) of FIG. 1 may also beimplemented with a variety of fabrics and protocols. Examples of suchfabrics include Ethernet (802.3), wireless (802.11), and the like.Examples of such data communications protocols include TransmissionControl Protocol (‘TCP’), User Datagram Protocol (‘UDP’), InternetProtocol (‘IP’), HyperText Transfer Protocol (‘HTTP’), Wireless AccessProtocol (‘WAP’), Handheld Device Transport Protocol (‘HDTP’), Real TimeProtocol (‘RTP’) and others as will occur to those of skill in the art.The LAN (160) depicted in FIG. 1 may be coupled to other computingdevices not illustrated in FIG. 1, for example, via the Internet (172).Although only one storage array (104) is expressly depicted as beingcoupled to the computing devices (164, 166, 168, 170) via the LAN (160),readers will appreciate that other storage arrays (102) in the storagesystem (100) may also be coupled to the computing devices (164, 166,168, 170) via the same LAN (160) or via a different LAN.

In addition to being coupled to the computing devices through the SAN(158) and the LAN (160), the storage arrays may also be coupled to oneor more cloud service providers, for example, through the Internet (172)or through another data communications network. One example cloudservice in FIG. 1 is a storage array services provider (176). Thestorage array service provider (176) may be configured to providevarious storage array services such as reporting of storage arrayperformance characteristics, configuration control of the storagearrays, analyzing log data generated by a storage system, and the like.The storage array services provider may rely on modules executing on thestorage array itself to gather such data.

Each storage array (102, 104) depicted in FIG. 1 includes a plurality ofstorage array controllers (106, 112, 118, 120). Each storage arraycontroller (106, 112, 118, 120) may be embodied as a module of automatedcomputing machinery comprising computer hardware, computer software, ora combination of computer hardware and software. Each storage arraycontroller (106, 112, 118, 120) may be configured to carry out variousstorage-related tasks such as, for example, writing data received fromthe one or more of the computing devices (164, 166, 168, 170) tostorage, erasing data from storage, retrieving data from storage toprovide the data to one or more of the computing devices (164, 166, 168,170), monitoring and reporting of disk utilization and performance,performing RAID (Redundant Array of Independent Drives) or RAID-likedata redundancy operations, compressing data, encrypting data, and soon.

Each storage array controller (106, 112, 118, 120) may be implemented ina variety of ways, including as a Field Programmable Gate Array(‘FPGA’), a Programmable Logic Chip (‘PLC’), an Application SpecificIntegrated Circuit (‘ASIC’), or computing device that includes discretecomponents such as a central processing unit, computer memory, andvarious adapters. Each storage array controller (106, 112, 118, 120) mayinclude, for example, a data communications adapter configured tosupport communications via the SAN (158) and the LAN (160). Althoughonly one of the storage array controllers (120) in the example of FIG. 1is depicted as being coupled to the LAN (160) for data communications,readers will appreciate that each storage array controller (106, 112,118, 120) may be independently coupled to the LAN (160). Each storagearray controller (106, 112, 118, 120) may also include, for example, anI/O controller or the like that couples the storage array controller(106, 112, 118, 120) for data communications, through a midplane (114,116), to a number of storage devices (146, 150), and a number of writebuffer devices (148, 152) that are utilized as write caches.

In the example depicted in FIG. 1, the presence of multiple storagearray controllers (106, 112, 118, 120) in each storage array (102, 104)can enable each storage array (102, 104) to be highly available as thereare independent, redundant storage array controllers (106, 112, 118,120) that are capable of servicing access requests (e.g., reads, writes)to the storage arrays (102, 104). In some embodiments, each storagearray controller (106, 112, 118, 120) in a particular storage array(102, 104) may appear to be active to the computing devices (164, 166,168, 170) as each storage array controller (106, 112, 118, 120) may beavailable for receiving requests to access the storage array (102, 104)from the computing devices (164, 166, 168, 170) via the SAN (158) or LAN(160). Although storage array controller (106, 112, 118, 120) may beavailable for receiving requests to access the storage array (102, 104),however, in some embodiments only one storage array controller (106,112, 118, 120) may actively be allowed to direct access requests to thestorage devices (146, 150) or write buffer devices (148, 152). For easeof explanation, a storage array controller that is allowed to directaccess requests to the storage devices (146, 150) or write bufferdevices (148, 152) may be referred to herein as an ‘active’ storagearray controller whereas a storage array controller that is not allowedto direct access requests to the storage devices (146, 150) or writebuffer devices (148, 152) may be referred to herein as a ‘passive’storage array controller. Readers will appreciate that because a passivestorage array controller may still receive requests to access thestorage array (102, 104) from the computing devices (164, 166, 168, 170)via the SAN (158) or LAN (160), the passive storage array controller maybe configured to forward any access requests received by the passivestorage array controller to the active storage array controller.

Consider an example in which a first storage array controller (106) in afirst storage array (102) is the active storage array controller that isallowed to direct access requests to the storage devices (146) or writebuffer devices (148) within the first storage array (102), while asecond storage array controller (118) in the first storage array (102)is the passive storage array controller that is not allowed to directaccess requests to the storage devices (146) or write buffer devices(148) within the first storage array (102). In such an example, thesecond storage array controller (118) may continue to receive accessrequests from the computing devices (164, 166, 168, 170) via the SAN(158) or LAN (160). Upon receiving access requests from the computingdevices (164, 166, 168, 170), the second storage array controller (118)may be configured to forward such access requests to the first storagearray controller (106) via a communications link between the firststorage array controller (106) and the second storage array controller(118). Readers will appreciate that such an embodiment may reduce theamount of coordination that must occur between the first storage arraycontroller (106) and the second storage array controller (118) relativeto an embodiment where both storage array controllers (106, 118) areallowed to simultaneously modify the contents of the storage devices(146) or write buffer devices (148).

Although the example described above refers to an embodiment where thefirst storage array controller (106) is the active storage arraycontroller while the second storage array controller (118) is thepassive storage array controller, over time such designations may switchback and forth. For example, an expected or unexpected event may occurthat results in a situation where the first storage array controller(106) is the passive storage array controller while the second storagearray controller (118) is the active storage array controller. Anexample of an unexpected event that could cause a change in the roles ofeach storage array controller (106, 118) is the occurrence of a failureor error condition with the first storage array controller (106) thatcauses the storage array (102) to fail over to the second storage arraycontroller (118). An example of an expected event that could cause achange in the roles of each storage array controller (106, 118) is theexpiration of a predetermined period of time, as the first storage arraycontroller (106) may be responsible for interacting with the storagedevices (146) and the write buffer devices (148) during a first timeperiod while the second storage array controller (118) may beresponsible for interacting with the storage devices (146) and the writebuffer devices (148) during a second time period. Readers willappreciate that although the preceding paragraphs describe active andpassive storage array controllers with reference to the first storagearray (102), the storage array controllers (112, 120) that are part ofother storage arrays (104) in the storage system (100) may operate in asimilar manner.

Each storage array (102, 104) depicted in FIG. 1 includes one or morewrite buffer devices (148, 152). Each write buffer device (148, 152) maybe configured to receive, from the one of the storage array controller(106, 112, 118, 120), data to be stored in one or more of the storagedevices (146, 150). In the example of FIG. 1, writing data to the writebuffer device (148, 152) may be carried out more quickly than writingdata to the storage device (146, 150). The storage array controllers(106, 112, 118, 120) may therefore be configured to effectively utilizethe write buffer devices (148, 152) as a quickly accessible buffer fordata destined to be written to one or the storage devices (146, 150). Byutilizing the write buffer devices (148, 152) in such a way, the writelatency experienced by users of the storage system (100) may besignificantly improved relative to storage systems that do not includesuch write buffer devices (148, 152). The write latency experienced byusers of the storage system (100) may be significantly improved relativeto storage systems that do not include such write buffer devices (148,152) because the storage array controllers (106, 112, 118, 120) may sendan acknowledgment to the user of the storage system (100) indicatingthat a write request has been serviced once the data associated with thewrite request has been written to one or the write buffer devices (148,152), even if the data associated with the write request has not yetbeen written to any of the storage devices (146, 150).

The presence of the write buffer devices (148, 152) may also improve theutilization of the storage devices (146, 150) as a storage arraycontroller (106, 112, 118, 120) can accumulate more writes and organizewriting to the storage devices (146, 150) for greater efficiency.Greater efficiency can be achieved, for example, as the storage arraycontroller (106, 112, 118, 120) may have more time to perform deepercompression of the data, the storage array controller (106, 112, 118,120) may be able to organize the data into write blocks that are inbetter alignment with the underlying physical storage on the storagedevices (146, 150), the storage array controller (106, 112, 118, 120)may be able to perform deduplication operations on the data, and so on.Such write buffer devices (148, 152) effectively convert storage arraysof solid-state drives (e.g., “Flash drives”) from latency limiteddevices to throughput limited devices. In such a way, the storage arraycontroller (106, 112, 118, 120) may be given more time to betterorganize what is written to the storage devices (146, 150), but afterdoing so, are not then mechanically limited like disk-based arrays are.

Each storage array (102, 104) depicted in FIG. 1 includes one or morestorage devices (146, 150). A ‘storage device’ as the term is used inthis specification refers to any device configured to record datapersistently. The term ‘persistently’ as used here refers to a device'sability to maintain recorded data after loss of a power source. Examplesof storage devices may include mechanical, spinning hard disk drives,solid-state drives, and the like.

The storage array controllers (106, 112) of FIG. 1 may be useful indynamically adjusting an amount of log data generated for a storagesystem according to some embodiments of the present disclosure. Thestorage array controllers (106, 112) may assist in dynamically adjustingan amount of log data generated for a storage system by: setting, for acomponent within the storage system, a logging level for the component,the logging level specifying the extent to which log data should begenerated for a particular component; determining, in dependence uponone or more measured operating characteristics of the storage system,whether the logging level for the component should be changed; andresponsive to determining that the logging level for the componentshould be changed, changing the logging level associated with thecomponent; as well as performing other functions as will be described ingreater detail below.

The arrangement of computing devices, storage arrays, networks, andother devices making up the example system illustrated in FIG. 1 are forexplanation, not for limitation. Systems useful according to variousembodiments of the present disclosure may include differentconfigurations of servers, routers, switches, computing devices, andnetwork architectures, not shown in FIG. 1, as will occur to those ofskill in the art.

Dynamically adjusting an amount of log data generated for a storagesystem in accordance with embodiments of the present disclosure isgenerally implemented with computers. In the system of FIG. 1, forexample, all the computing devices (164, 166, 168, 170) and storagecontrollers (106, 112, 118, 120) may be implemented to some extent atleast as computers. For further explanation, therefore, FIG. 2 setsforth a block diagram of a storage array controller (202) useful indynamically adjusting an amount of log data generated for a storagesystem according to some embodiments of the present disclosure.

The storage array controllers (202, 206) depicted in FIG. 2 may besimilar to the storage array controllers depicted in FIG. 1, as thestorage array controllers (202, 206) of FIG. 2 may be communicativelycoupled, via a midplane (210), to one or more storage devices (216) andto one or more write buffer devices (218) that are included as part of astorage array (220). The storage array controllers (202, 206) may becoupled to the midplane (210) via one or more data communications links(204, 208) and the midplane (206) may be coupled to the storage devices(216) and the memory buffer devices (218) via one or more datacommunications links (212, 214). The data communications links (204,208, 212, 214) of FIG. 2 may be embodied, for example, as a PeripheralComponent Interconnect Express (‘PCIe’) bus, as a Serial Attached SCSI(‘SAS’) data communications link, and so on. Although only one of thestorage array controllers (202) is depicted in detail, readers willappreciate that other storage array controllers (206) may includesimilar components. For ease of explanation, however, the detailed viewof one of the storage array controllers (202) will be described below.

The storage array controller (202) detailed in FIG. 2 can include atleast one computer processor (240) or ‘CPU’ as well as random accessmemory (‘RAM’) (244). The computer processor (240) may be connected tothe RAM (244) via a data communications link (238), which may beembodied as a high speed memory bus such as a Double-Data Rate 4(‘DDR4’) bus. Although the storage array controller (202) detailed inFIG. 2 includes only a single computer processor, however, readers willappreciate that storage array controllers useful in dynamicallyadjusting an amount of log data generated for a storage system accordingto some embodiments of the present disclosure may include additionalcomputer processors. Likewise, although the storage array controller(202) detailed in FIG. 2 includes only a RAM (244), readers willappreciate that storage array controllers useful in dynamicallyadjusting an amount of log data generated for a storage system accordingto some embodiments of the present disclosure may include additionalforms of computer memory such as flash memory.

The storage array controller (202) detailed in FIG. 2 includes anoperating system (246) that is stored in RAM (246). Examples ofoperating systems useful in storage array controllers (202, 206)configured for [dynamically adjusting an amount of log data generatedfor a storage system according to some embodiments of the presentdisclosure include UNIX™, Linux™ Microsoft Windows™, and others as willoccur to those of skill in the art. The operating system (246) depictedin FIG. 2 may be embodied, for example, as system software that managescomputer hardware and software resources on the storage array controller(202).

The storage array controller (202) detailed in FIG. 2 also includes anarray operating environment (252) that is stored in RAM (252). The arrayoperating environment (252) may be embodied as one or more modules ofcomputer program instructions used to enable the storage arraycontroller (202) to service access requests that are directed to thestorage array (220). The array operating environment (252) may beresponsible for generating I/O requests (e.g., read requests, writerequests) that are sent to the storage devices (216) or the write bufferdevices (218). The array operating environment (252) may be furtherconfigured to perform various functions that result in more efficientutilization of the resources within the storage array (220). The arrayoperating environment (252) may be configured, for example, to compressdata prior to writing the data to one of the storage devices (216), toperform data deduplication operations, to pool data that is to bewritten to one of the storage devices (216) so that data may be writtenin blocks of a predetermined size, and so on.

The storage array controller (202) detailed in FIG. 2 also includes alog management module (256), a module that includes computer programinstructions useful in dynamically adjusting an amount of log datagenerated for a storage system according to some embodiments of thepresent disclosure. The log management module (256) may include computerprogram instructions that, when executed, cause the storage arraycontroller (202) to set, for a component within the storage system, alogging level for the component, the logging level specifying the extentto which log data should be generated for a particular component;determine, in dependence upon one or more measured operatingcharacteristics of the storage system, whether the logging level for thecomponent should be changed; change the logging level associated withthe component in response to determining that the logging level for thecomponent should be changed; and perform other functions as will bedescribed in greater detail below.

The storage array controller (202) detailed in FIG. 2 also includes aplurality of host bus adapters (222, 224, 250) and Ethernet adapters(226, 228) that are coupled to the computer processor (240) via a datacommunications link (230, 232, 236, 238, 258). Each host bus adapter(222, 224, 250) may be embodied as a module of computer hardware thatconnects the host system (i.e., the storage array controller) to othernetwork and storage devices. Each of the host bus adapters (222, 224,250) of FIG. 2 may be embodied, for example, as a Fibre Channel adapterthat enables the storage array controller (202) to connect to a SAN, asan Ethernet adapter that enables the storage array controller (202) toconnect to a LAN, as a Target Channel Adapter, as a SCSI/Storage TargetAdapter, and so on. Each of the host bus adapters (222, 224, 250) may becoupled to the computer processor (240) via a data communications link(230, 232, 258) such as, for example, a PCIe bus.

The storage array controller (202) detailed in FIG. 2 also includes aswitch (254) that is coupled to the computer processor (240) via a datacommunications link (248). The switch (254) of FIG. 2 may be embodied asa computer hardware device that can create multiple endpoints out of asingle endpoint, thereby enabling multiple devices to share what wasinitially a single endpoint. The switch (254) of FIG. 2 may be embodied,for example, as a PCIe switch that is coupled to a PCIe bus and presentsmultiple PCIe connection points to the midplane (210).

The storage array controller (202) of FIG. 2 may also include a datacommunications link (242) for coupling the storage array controller(202) to other storage array controllers (206). Such a datacommunications link (242) may be embodied, for example, as a QuickPathInterconnect (‘QPI’) interconnect, as PCIe non-transparent bridge(‘NTB’) interconnect, and so on.

Readers will recognize that these components, protocols, adapters, andarchitectures are for illustration only, not limitation. Such a storagearray controller may be implemented in a variety of different ways, eachof which is well within the scope of the present disclosure.

For further explanation, FIG. 3 sets forth a block diagram illustratinga write buffer device (312) useful in storage systems configured fordynamically adjusting an amount of log data generated according to someembodiments of the present disclosure. The write buffer device (312)depicted in FIG. 3 is similar to the write buffer devices depicted inFIG. 1 and FIG. 2. The write buffer device (312) may be included in astorage array (302) that includes a plurality of storage arraycontrollers (304, 306) that are communicatively coupled to a pluralityof storage devices (310) and also communicatively coupled to a pluralityof write buffer devices (312) via a midplane (308).

The write buffer device (312) depicted in FIG. 3 includes two datacommunications ports (314, 316). The data communications ports (314,316) of FIG. 3 may be embodied, for example, as computer hardware forcommunicatively coupling the write buffer device (312) to a storagearray controller (304, 306) via the midplane (308). For example, thewrite buffer device (312) may be communicatively coupled to the firststorage array controller (304) via a first data communications port(314) and the write buffer device (312) may also be communicativelycoupled to the second storage array controller (306) via a second datacommunications port (316). Although the write buffer device (312)depicted in FIG. 3 includes two data communications ports (314, 316),readers will appreciate that write buffer devices useful for bufferingdata to be written to an array of non-volatile storage devices mayinclude only one data communications port or, alternatively, additionaldata communications ports not depicted in FIG. 3.

The write buffer device (312) depicted in FIG. 3 also includes acontroller (320). The controller (320) depicted in FIG. 3 may beembodied, for example, as computer hardware for receiving memory accessrequests (e.g., a request to write data to memory in the write bufferdevice) via the data communications ports (314, 316) and servicing suchmemory access requests. The controller (320) depicted in FIG. 3 may beembodied, for example, as an ASIC, as a microcontroller, and so on. Thecontroller (320) depicted in FIG. 3 may be communicatively coupled thedata communications ports (314, 316), for example, via a PCIe datacommunications bus.

The write buffer device (312) depicted in FIG. 3 also includes aplurality of DRAM memory modules, embodied in FIG. 3 as DRAM dualin-line memory modules (‘DIMMs’) (338). The DRAM DIMMs (338) depicted inFIG. 3 may be coupled to the controller (320) via a memory bus such as aDDR (318) memory bus such that the controller (320) can be configured towrite data to the DRAM DIMMs (338) via the DDR (318) memory bus.

The write buffer device (312) depicted in FIG. 3 also includes a primarypower source (326). The primary power source (326) may be embodied ascomputer hardware for providing electrical power to the computingcomponents that are within the write buffer device (312). The primarypower source (326) may be embodied, for example, as a switched-modepower supply that supplies electric energy to an electrical load byconverting alternating current (‘AC’) power from a mains supply to adirect current (‘DC’) power, as a DC-to-DC converter that converts asource of direct current (DC) from one voltage level to another, and soon. The primary power source (326) of FIG. 3 is coupled to thecontroller (320) via a power line (322) that the primary power source(326) can use to deliver power to the controller (320). The primarypower source (326) of FIG. 3 is also coupled to the DRAM DIMMs (338) viaa power line (330) that the primary power source (326) can use todeliver power to the DRAM DIMMs (338). The primary power source (326) ofFIG. 3 is also coupled to a power source controller (340) via a powerline (332) that the primary power source (326) can use to deliver powerto the power source controller (340). The primary power source (326) canmonitor which components are receiving power through the use of one ormore control lines (324), serial presence detect (‘SPD’) lines (328), orother mechanism for detecting the presence of a device and detectingthat power is being provided to the device. Readers will appreciate thatwrite devices useful for buffering data to be written to an array ofnon-volatile storage devices may include additional computing componentsnot depicted in FIG. 3, each of which may also receive power from theprimary power source (326).

The write buffer device (312) depicted in FIG. 3 also includes a backuppower source (344). The backup power source (344) depicted in FIG. 3represents a power source capable of providing power to the DRAM DIMMs(338) in the event that the primary power source (326) fails. In such away, the DRAM DIMMs (338) may effectively serve as non-volatile memory,as a failure of the primary power source (326) will not cause thecontents of the DRAM DIMMs (338) to be lost because the DRAM DIMMs (338)will continue to receive power from the backup power source (344). Sucha backup power source (344) may be embodied, for example, as asupercapacitor.

The write buffer device (312) depicted in FIG. 3 also includes a powersource controller (340). The power source controller (340) depicted inFIG. 3 may be embodied as a module of computer hardware configured toidentify a failure of the primary power source (326) and to cause powerto be delivered to the DRAM DIMMs (338) from the backup power source(344). In such an example, power may be delivered to the DRAM DIMMs(338) from the backup power source (344) via a first power line (342)between the power source controller (340) and the backup power source(344), as well as a second power line (334) between the backup powersource controller (340) and the DRAM DIMMs (338). The backup powersource controller (340) depicted in FIG. 3 may be embodied, for example,as an analog circuit, an ASIC, a microcontroller, and so on. The powersource controller (340) can monitor whether the DRAM DIMMs (338) havepower through the use of one or more control lines (336) that may becoupled to the DRAM DIMMs (338), as well as one or more control linesthat may be coupled to the primary power source (326). In such anexample, by exchanging signals between the DRAM DIMMs (338), the primarypower source (326), and the power source controller (340), the powersource controller (340) may identify whether power is being provided tothe DRAM DIMMs (338) by the primary power source (326).

In the example depicted in FIG. 3, the controller (320) may beconfigured to receive, from a storage array controller (304, 306) viathe one or more data communications ports (314, 316), an instruction towrite data to the one or more DRAM DIMMs (338). Such an instruction mayinclude, for example, the location at which to write the data, the datato be written to the DRAM DIMMs (338), the identity of the host thatissued the instruction, the identity of a user associated with theinstruction, or any other information needed to service the instruction.In the example depicted in FIG. 3, the NVRAM controller (320) may befurther configured to write the data to the one or more DRAM DIMMs (338)in response to receiving such an instruction.

In the example depicted in FIG. 3, the controller (320) may be furtherconfigured to send an acknowledgment indicating that the data has beenwritten to the array (302) of non-volatile storage devices in responseto writing the data to the one or more DRAM DIMMs (338). The controller(320) may send the acknowledgment indicating that the data has beenwritten to the array (302) of non-volatile storage devices in responseto writing the data to the DRAM DIMMs (338) in the write buffer device(312). Readers will appreciate that although some forms of DRAM DIMMs(338) are considered to be volatile memory, because the DRAM DIMMs (338)are backed by redundant power sources (326, 344), writing the data tothe DRAM DIMMs (338) in the write buffer device (312) may be treated thesame as writing the data to traditional forms of non-volatile memorysuch as the storage devices (310). Furthermore, the DRAM DIMMs (338) inthe write buffer device (312) can include one or more NVDIMMs. As such,once the data has been written to the DRAM DIMMs (338) in the writebuffer device (312), an acknowledgement may be sent indicating that thedata has been safely and persistently written to the array (302) ofnon-volatile storage devices.

In the example depicted in FIG. 3, the controller (320) may be furtherconfigured to determine whether the primary power source (326) hasfailed. The controller (320) may determine whether the primary powersource (326) has failed, for example, by receiving a signal over thecontrol line (324) indicating that the primary power source (326) hasfailed or is failing, by detecting a lack of power from the primarypower source (326), and so on. In such an example, the controller (320)may be coupled to the backup power source (344) or may have access toanother source of power such that the controller (320) can remainoperational if the primary power source (326) does fail.

In the example depicted in FIG. 3, the controller (320) may be furtherconfigured to initiate a transfer of data contained in the one or moreDRAM DIMMs (338) to flash memory in the write buffer device (312) inresponse to determining that the primary power source (326) has failed.The controller (320) may initiate a transfer of data contained in theone or more DRAM DIMMs (338) to flash memory in the write buffer device(312), for example, by signaling an NVDIMM to write the data containedin the one or more DRAM DIMMs (338) to flash memory on the NVDIMM, byreading the data contained in the one or more DRAM DIMMs (338) andwriting such data to flash memory in the write buffer device (312), orin other ways.

The embodiments below describe a storage cluster that stores user data,such as user data originating from one or more user or client systems orother sources external to the storage cluster. The storage cluster candistribute user data across storage nodes housed within a chassis, forexample, using erasure coding and redundant copies of metadata. Erasurecoding refers to a method of data protection or reconstruction in whichdata is stored across a set of different locations, such as disks,storage nodes, geographic locations, and so on. Flash memory is one typeof solid-state memory that may be integrated with the embodiments,although the embodiments may be extended to other types of solid-statememory or other storage medium, including non-solid state memory.Control of storage locations and workloads may be distributed across thestorage locations in a clustered peer-to-peer system. Tasks such asmediating communications between the various storage nodes, detectingwhen a storage node has become unavailable, and balancing I/Os (inputsand outputs) across the various storage nodes, may all be handled on adistributed basis. Data may be laid out or distributed across multiplestorage nodes in data fragments or stripes that support data recovery insome embodiments. Ownership of data can be reassigned within a cluster,independent of input and output patterns. This architecture described inmore detail below allows a storage node in the cluster to fail, with thesystem remaining operational, since the data can be reconstructed fromother storage nodes and thus remain available for input and outputoperations. In various embodiments, a storage node may be referred to asa cluster node, a blade, or a server.

The storage cluster may be contained within a chassis, i.e., anenclosure housing one or more storage nodes. A mechanism to providepower to each storage node, such as a power distribution bus, and acommunication mechanism, such as a communication bus that enablescommunication between the storage nodes may be included within thechassis. The storage cluster can run as an independent system in onelocation according to some embodiments. In one embodiment, a chassiscontains at least two instances of both the power distribution and thecommunication bus which may be enabled or disabled independently. Theinternal communication bus may be an Ethernet bus, however, othertechnologies such as PCIe, InfiniBand, and others, are suitable. Thechassis can provide a port for an external communication bus forenabling communication between multiple chassis, directly or through aswitch, and with client systems. The external communication may use atechnology such as Ethernet, InfiniBand, Fibre Channel, etc. In someembodiments, the external communication bus uses different communicationbus technologies for inter-chassis and client communication. If a switchis deployed within or between chassis, the switch may act as atranslation between multiple protocols or technologies. When multiplechassis are connected to define a storage cluster, the storage clustermay be accessed by a client using either proprietary interfaces orstandard interfaces such as NFS, common internet file system (CIFS),SCSI, HTTP, or other suitable interface. Translation from the clientprotocol may occur at the switch, chassis external communication bus orwithin each storage node.

Each storage node may be one or more storage servers and each storageserver may be connected to one or more non-volatile solid state memoryunits, which may be referred to as storage units or storage devices. Oneembodiment includes a single storage server in each storage node andbetween one to eight non-volatile solid state memory units, however thisone example is not meant to be limiting. The storage server may includea processor, DRAM, and interfaces for the internal communication bus andpower distribution for each of the power buses. Inside the storage node,the interfaces and storage unit may share a communication bus, e.g., PCIExpress, in some embodiments. The non-volatile solid state memory unitsmay directly access the internal communication bus interface through astorage node communication bus, or request the storage node to accessthe bus interface. The non-volatile solid state memory unit may containan embedded CPU, solid state storage controller, and a quantity of solidstate mass storage, e.g., between 2-32 terabytes (TB) in someembodiments. An embedded volatile storage medium, such as DRAM, and anenergy reserve apparatus may be included in the non-volatile solid statememory unit. In some embodiments, the energy reserve apparatus is acapacitor, super-capacitor, or battery that enables transferring asubset of DRAM contents to a stable storage medium in the case of powerloss. In some embodiments, the non-volatile solid state memory unit isconstructed with a storage class memory, such as phase change ormagnetoresistive random access memory (MRAM) that substitutes for DRAMand enables a reduced power hold-up apparatus.

One of many features of the storage nodes and non-volatile solid statestorage may be the ability to proactively rebuild data in a storagecluster. The storage nodes and non-volatile solid state storage may beable to determine when a storage node or non-volatile solid statestorage in the storage cluster is unreachable, independent of whetherthere is an attempt to read data involving that storage node ornon-volatile solid state storage. The storage nodes and non-volatilesolid state storage may then cooperate to recover and rebuild the datain at least partially new locations. This constitutes a proactiverebuild, in that the system rebuilds data without waiting until the datais needed for a read access initiated from a client system employing thestorage cluster. These and further details of the storage memory andoperation thereof are discussed below.

FIG. 4 illustrates a perspective view of a storage cluster (402), withmultiple storage nodes (412) and internal solid-state memory coupled toeach storage node to provide network attached storage or storage areanetwork, in accordance with some embodiments. A network attachedstorage, storage area network, or a storage cluster, or other storagememory, could include one or more storage clusters (402), each havingone or more storage nodes (412), in a flexible and reconfigurablearrangement of both the physical components and the amount of storagememory provided thereby. The storage cluster (402) may be designed tofit in a rack, and one or more racks can be set up and populated asdesired for the storage memory. The storage cluster (402) may include achassis (404) having multiple slots (424). It should be appreciated thatchassis (404) may be referred to as a housing, enclosure, or rack unit.In one embodiment, the chassis (404) has fourteen slots (424), althoughother numbers of slots are readily devised. For example, someembodiments have four slots, eight slots, sixteen slots, thirty-twoslots, or other suitable number of slots. Each slot (424) canaccommodate one storage node (412) in some embodiments. The chassis(404) may include flaps (406) that can be utilized to mount the chassis(404) on a rack. Fans (410) may provide air circulation for cooling ofthe storage nodes (412) and components thereof, although other coolingcomponents could be used, or an embodiment could be devised withoutcooling components. A switch fabric (408) may couple storage nodes (412)within chassis (404) together and to a network for communication to thememory. In an embodiment depicted in FIG. 4, the slots (424) to the leftof the switch fabric (408) and fans (410) are shown occupied by storagenodes (1012), while the slots (424) to the right of the switch fabric(408) and fans (410) are empty and available for insertion of storagenode (412) for illustrative purposes. This configuration is one example,and one or more storage nodes (412) could occupy the slots (424) invarious further arrangements. The storage node arrangements need not besequential or adjacent in some embodiments. Storage nodes (412) may behot pluggable, meaning that a storage node (412) can be inserted into aslot (424) in the chassis (404), or removed from a slot (424), withoutstopping or powering down the system. Upon insertion or removal of astorage node (412) from a slot (424), the system may automaticallyreconfigure in order to recognize and adapt to the change.Reconfiguration, in some embodiments, includes restoring redundancyand/or rebalancing data or load.

Each storage node (412) can have multiple components. In the embodimentshown here, the storage node (412) includes a printed circuit board(422) populated by a CPU (416), i.e., processor, a memory (414) coupledto the CPU (416), and a non-volatile solid state storage (418) coupledto the CPU (416), although other mountings and/or components could beused in further embodiments. The memory (414) may include instructionswhich are executed by the CPU (416) and/or data operated on by the CPU(416). As further explained below, the non-volatile solid state storage(418) may include flash or, in further embodiments, other types ofsolid-state memory.

Referring to FIG. 4, the storage cluster (402) may be scalable, meaningthat storage capacity with non-uniform storage sizes may be readilyadded, as described above. One or more storage nodes (412) can beplugged into or removed from each chassis and the storage clusterself-configures in some embodiments. Plug-in storage nodes (412),whether installed in a chassis as delivered or later added, can havedifferent sizes. For example, in one embodiment a storage node (412) canhave any multiple of 4 TB, e.g., 8 TB, 12 TB, 16 TB, 32 TB, etc. Infurther embodiments, a storage node (412) could have any multiple ofother storage amounts or capacities. Storage capacity of each storagenode (412) may be broadcast, and may influence decisions of how tostripe the data. For maximum storage efficiency, an embodiment canself-configure as wide as possible in the stripe, subject to apredetermined requirement of continued operation with loss of up to one,or up to two, non-volatile solid state storage (418) units or storagenodes (412) within the chassis.

FIG. 5 illustrates a block diagram showing a communications interconnect(504) and power distribution bus (506) coupling multiple storage nodes(412) according to some embodiments of the present disclosure. Referringback to FIG. 4, the communications interconnect (504) can be included inor implemented with the switch fabric (408) in some embodiments. Wheremultiple storage clusters occupy a rack, the communications interconnect(504) can be included in or implemented with a top of rack switch, insome embodiments. In the example depicted in FIG. 5, the storage clustermay be enclosed within a single chassis (404). An external port (510)may be coupled to storage nodes (412) through the communicationsinterconnect (504), while another external port (512) may be coupleddirectly to a storage node (412). An external power port (508) may becoupled to a power distribution bus (506). The storage nodes (412) mayinclude varying amounts and differing capacities of non-volatile solidstate storage (418) as described with reference to FIG. 4. In addition,one or more storage nodes (412) may be a compute only storage node asillustrated in FIG. 5. Authorities (502) may be implemented on thenon-volatile solid state storage (418), for example as lists or otherdata structures stored in memory. In some embodiments the authoritiesmay be stored within the non-volatile solid state storage (418) andsupported by software executing on a controller or other processor ofthe non-volatile solid state storage (418). In a further embodiment, theauthorities (502) may be implemented on the storage nodes (412), forexample, as lists or other data structures stored in memory andsupported by software executing on a CPU of the storage node (412). Theauthorities (502) may control how and where data is stored in thenon-volatile solid state storage (418) in some embodiments. This controlmay assist in determining which type of erasure coding scheme is appliedto the data, and which storage nodes (412) have which portions of thedata. Each authority (502) may be assigned to a non-volatile solid statestorage (418). Each authority may also control a range of inode numbers,segment numbers, or other data identifiers which are assigned to data bya file system, by the storage nodes (412), or by the non-volatile solidstate storage (418), in various embodiments.

Every piece of data, and every piece of metadata, may have redundancy inthe system in some embodiments. In addition, every piece of data andevery piece of metadata may have an owner, which may be referred to asan authority (502). If that authority (502) is unreachable, for examplethrough failure of a storage node (412), there may be a plan ofsuccession for how to find that data or that metadata. In variousembodiments, there are redundant copies of authorities (502).Authorities (502) may have a relationship to storage nodes (412) and tonon-volatile solid state storage (418) in some embodiments. Eachauthority (502), covering a range of data segment numbers or otheridentifiers of the data, may be assigned to a specific non-volatilesolid state storage (418). In some embodiments the authorities (502) forall of such ranges are distributed over the non-volatile solid statestorage (418) of a storage cluster. Each storage node (412) may have anetwork port that provides access to the non-volatile solid statestorage (418) of that storage node (412). Data can be stored in asegment, which is associated with a segment number and that segmentnumber is an indirection for a configuration of a RAID stripe in someembodiments. The assignment and use of the authorities (502) maytherefore establish an indirection to data. Indirection may be referredto as the ability to reference data indirectly, in this case via anauthority (502), in accordance with some embodiments. A segment mayidentify a set of non-volatile solid state storage (418) and a localidentifier into the set of non-volatile solid state storage (418) thatmay contain data. In some embodiments, the local identifier is an offsetinto the device and may be reused sequentially by multiple segments. Inother embodiments the local identifier is unique for a specific segmentand never reused. The offsets in the non-volatile solid state storage(418) may be applied to locating data for writing to or reading from thenon-volatile solid state storage (418) (in the form of a RAID stripe).Data may be striped across multiple units of non-volatile solid statestorage (418), which may include or be different from the non-volatilesolid state storage (418) having the authority (502) for a particulardata segment.

If there is a change in where a particular segment of data is located,e.g., during a data move or a data reconstruction, the authority (502)for that data segment may be consulted, at that non-volatile solid statestorage (418) or storage node (412) having that authority (502). Inorder to locate a particular piece of data, embodiments calculate a hashvalue for a data segment or apply an inode number or a data segmentnumber. The output of this operation points to a non-volatile solidstate storage (418) having the authority (502) for that particular pieceof data. In some embodiments there are two stages to this operation. Thefirst stage maps an entity identifier (ID), e.g., a segment number,inode number, or directory number to an authority identifier. Thismapping may include a calculation such as a hash or a bit mask. Thesecond stage is mapping the authority identifier to a particularnon-volatile solid state storage (418), which may be done through anexplicit mapping. The operation is repeatable, so that when thecalculation is performed, the result of the calculation repeatably andreliably points to a particular non-volatile solid state storage (418)having that authority (502). The operation may include the set ofreachable storage nodes as input. If the set of reachable non-volatilesolid state storage units changes the optimal set changes. In someembodiments, the persisted value is the current assignment (which isalways true) and the calculated value is the target assignment thecluster will attempt to reconfigure towards. This calculation may beused to determine the optimal non-volatile solid state storage (418) foran authority in the presence of a set of non-volatile solid statestorage (418) that are reachable and constitute the same cluster. Thecalculation also determines an ordered set of peer non-volatile solidstate storage (418) that will also record the authority to non-volatilesolid state storage mapping so that the authority may be determined evenif the assigned non-volatile solid state storage is unreachable. Aduplicate or substitute authority (502) may be consulted if a specificauthority (502) is unavailable in some embodiments.

With reference to FIGS. 4 and 5, two of the many tasks of the CPU (416)on a storage node (412) are to break up write data and reassemble readdata. When the system has determined that data is to be written, theauthority (502) for that data is located as above. When the segment IDfor data is already determined the request to write is forwarded to thenon-volatile solid state storage (418) currently determined to be thehost of the authority (502) determined from the segment. The host CPU(416) of the storage node (412), on which the non-volatile solid statestorage (418) and corresponding authority (502) reside, may then breaksup or shard the data and transmits the data out to various non-volatilesolid state storage (418). The transmitted data may be written as a datastripe in accordance with an erasure coding scheme. In some embodiments,data is requested to be pulled, and in other embodiments, data ispushed. In reverse, when data is read, the authority (502) for thesegment ID containing the data is located as described above. The hostCPU (416) of the storage node (412) on which the non-volatile solidstate storage (418) and corresponding authority (502) reside may requestthe data from the non-volatile solid state storage and correspondingstorage nodes pointed to by the authority. In some embodiments the datais read from flash storage as a data stripe. The host CPU (416) ofstorage node (412) may then reassemble the read data, correcting anyerrors (if present) according to the appropriate erasure coding scheme,and forward the reassembled data to the network. In further embodiments,some or all of these tasks can be handled in the non-volatile solidstate storage (418). In some embodiments, the segment host requests thedata be sent to storage node (412) by requesting pages from storage andthen sending the data to the storage node making the original request.

In some systems, for example in UNIX-style file systems, data is handledwith an index node or inode, which specifies a data structure thatrepresents an object in a file system. The object could be a file or adirectory, for example. Metadata may accompany the object, as attributessuch as permission data and a creation timestamp, among otherattributes. A segment number could be assigned to all or a portion ofsuch an object in a file system. In other systems, data segments arehandled with a segment number assigned elsewhere. For purposes ofdiscussion, the unit of distribution may be an entity, and an entity canbe a file, a directory or a segment. That is, entities are units of dataor metadata stored by a storage system. Entities may be grouped intosets called authorities. Each authority may have an authority owner,which is a storage node that has the exclusive right to update theentities in the authority. In other words, a storage node may containthe authority, and that the authority may, in turn, contain entities.

A segment may be a logical container of data in accordance with someembodiments. A segment may be an address space between medium addressspace and physical flash locations, i.e., the data segment number, arein this address space. Segments may also contain meta-data, which enabledata redundancy to be restored (rewritten to different flash locationsor devices) without the involvement of higher level software. In oneembodiment, an internal format of a segment contains client data andmedium mappings to determine the position of that data. Each datasegment may be protected, e.g., from memory and other failures, bybreaking the segment into a number of data and parity shards, whereapplicable. The data and parity shards may be distributed, i.e.,striped, across non-volatile solid state storage (418) coupled to thehost CPUs (416) in accordance with an erasure coding scheme. Usage ofthe term segments refers to the container and its place in the addressspace of segments in some embodiments. Usage of the term stripe refersto the same set of shards as a segment and includes how the shards aredistributed along with redundancy or parity information in accordancewith some embodiments.

A series of address-space transformations may take place across anentire storage system. At the top may be the directory entries (filenames) which link to an inode. Modes may point into medium addressspace, where data is logically stored. Medium addresses may be mappedthrough a series of indirect mediums to spread the load of large files,or implement data services like deduplication or snapshots. Mediumaddresses may be mapped through a series of indirect mediums to spreadthe load of large files, or implement data services like deduplicationor snapshots. Segment addresses may then be translated into physicalflash locations. Physical flash locations may have an address rangebounded by the amount of flash in the system in accordance with someembodiments. Medium addresses and segment addresses may be logicalcontainers, and in some embodiments use a 128 bit or larger identifierso as to be practically infinite, with a likelihood of reuse calculatedas longer than the expected life of the system. Addresses from logicalcontainers are allocated in a hierarchical fashion in some embodiments.Initially, each non-volatile solid state storage (418) unit may beassigned a range of address space. Within this assigned range, thenon-volatile solid state storage (418) may be able to allocate addresseswithout synchronization with other non-volatile solid state storage(418).

Data and metadata may be stored by a set of underlying storage layoutsthat are optimized for varying workload patterns and storage devices.These layouts may incorporate multiple redundancy schemes, compressionformats and index algorithms. Some of these layouts may storeinformation about authorities and authority masters, while others maystore file metadata and file data. The redundancy schemes may includeerror correction codes that tolerate corrupted bits within a singlestorage device (such as a NAND flash chip), erasure codes that toleratethe failure of multiple storage nodes, and replication schemes thattolerate data center or regional failures. In some embodiments, lowdensity parity check (LDPC) code is used within a single storage unit.Reed-Solomon encoding may be used within a storage cluster, andmirroring may be used within a storage grid in some embodiments.Metadata may be stored using an ordered log structured index (such as aLog Structured Merge Tree), and large data may not be stored in a logstructured layout.

In order to maintain consistency across multiple copies of an entity,the storage nodes may agree implicitly on two things throughcalculations: (1) the authority that contains the entity, and (2) thestorage node that contains the authority. The assignment of entities toauthorities can be done by pseudo randomly assigning entities toauthorities, by splitting entities into ranges based upon an externallyproduced key, or by placing a single entity into each authority.Examples of pseudorandom schemes are linear hashing and the ReplicationUnder Scalable Hashing (RUSH) family of hashes, including ControlledReplication Under Scalable Hashing (CRUSH). In some embodiments,pseudo-random assignment is utilized only for assigning authorities tonodes because the set of nodes can change. The set of authorities cannotchange so any subjective function may be applied in these embodiments.Some placement schemes automatically place authorities on storage nodes,while other placement schemes rely on an explicit mapping of authoritiesto storage nodes. In some embodiments, a pseudorandom scheme is utilizedto map from each authority to a set of candidate authority owners. Apseudorandom data distribution function related to CRUSH may assignauthorities to storage nodes and create a list of where the authoritiesare assigned. Each storage node has a copy of the pseudorandom datadistribution function, and can arrive at the same calculation fordistributing, and later finding or locating an authority. Each of thepseudorandom schemes requires the reachable set of storage nodes asinput in some embodiments in order to conclude the same target nodes.Once an entity has been placed in an authority, the entity may be storedon physical devices so that no expected failure will lead to unexpecteddata loss. In some embodiments, rebalancing algorithms attempt to storethe copies of all entities within an authority in the same layout and onthe same set of machines.

Examples of expected failures include device failures, stolen machines,datacenter fires, and regional disasters, such as nuclear or geologicalevents. Different failures may lead to different levels of acceptabledata loss. In some embodiments, a stolen storage node impacts neitherthe security nor the reliability of the system, while depending onsystem configuration, a regional event could lead to no loss of data, afew seconds or minutes of lost updates, or even complete data loss.

In the embodiments, the placement of data for storage redundancy may beindependent of the placement of authorities for data consistency. Insome embodiments, storage nodes that contain authorities may not containany persistent storage. Instead, the storage nodes may be connected tonon-volatile solid state storage units that do not contain authorities.The communications interconnect between storage nodes and non-volatilesolid state storage units can consist of multiple communicationtechnologies and has non-uniform performance and fault tolerancecharacteristics. In some embodiments, as mentioned above, non-volatilesolid state storage units are connected to storage nodes via PCIexpress, storage nodes are connected together within a single chassisusing Ethernet backplane, and chassis are connected together to form astorage cluster. Storage clusters may be connected to clients usingEthernet or fiber channel in some embodiments. If multiple storageclusters are configured into a storage grid, the multiple storageclusters are connected using the Internet or other long-distancenetworking links, such as a “metro scale” link or private link that doesnot traverse the internet.

Authority owners may have the exclusive right to modify entities, tomigrate entities from one non-volatile solid state storage unit toanother non-volatile solid state storage unit, and to add and removecopies of entities. This allows for maintaining the redundancy of theunderlying data. When an authority owner fails, is going to bedecommissioned, or is overloaded, the authority may be transferred to anew storage node. Transient failures can make it non-trivial to ensurethat all non-faulty machines agree upon the new authority location. Theambiguity that arises due to transient failures can be achievedautomatically by a consensus protocol such as Paxos, hot-warm failoverschemes, via manual intervention by a remote system administrator, or bya local hardware administrator (such as by physically removing thefailed machine from the cluster, or pressing a button on the failedmachine). In some embodiments, a consensus protocol is used, andfailover is automatic. If too many failures or replication events occurin too short a time period, the system may go into a self-preservationmode and halt replication and data movement activities until anadministrator intervenes in accordance with some embodiments.

Persistent messages may be persistently stored prior to beingtransmitted. This allows the system to continue to serve client requestsdespite failures and component replacement. Although many hardwarecomponents contain unique identifiers that are visible to systemadministrators, manufacturer, hardware supply chain and ongoingmonitoring quality control infrastructure, applications running on topof the infrastructure address may virtualize addresses. Thesevirtualized addresses may not change over the lifetime of the storagesystem, regardless of component failures and replacements. This allowseach component of the storage system to be replaced over time withoutreconfiguration or disruptions of client request processing.

In some embodiments, the virtualized addresses are stored withsufficient redundancy. A continuous monitoring system may correlatehardware and software status and the hardware identifiers. This allowsdetection and prediction of failures due to faulty components andmanufacturing details. The monitoring system may also enable theproactive transfer of authorities and entities away from impacteddevices before failure occurs by removing the component from thecritical path in some embodiments.

FIG. 6 is a multiple level block diagram, showing contents of a storagenode (412) and contents of a non-volatile solid state storage (418) ofthe storage node (412) according to some embodiments of the presentdisclosure. Data may be communicated to and from the storage node (412)by a network interface controller (NIC) (602) in some embodiments. Eachstorage node (412) may include a CPU (416), and one or more non-volatilesolid state storage (418), as discussed above. Moving down one level inFIG. 6, each non-volatile solid state storage (418) may have arelatively fast non-volatile solid state memory, such as NVRAM (604),and flash memory (606). In some embodiments, NVRAM (604) may be acomponent that does not require program/erase cycles (DRAM, MRAM, PCM),and can be a memory that can support being written vastly more oftenthan the memory is read from. Moving down another level in FIG. 6, theNVRAM (604) may be implemented in one embodiment as high speed volatilememory, such as DRAM (616), backed up by an energy reserve (618). Theenergy reserve (618) may provide sufficient electrical power to keep theDRAM (616) powered long enough for contents to be transferred to theflash memory (606) in the event of power failure. In some embodiments,the energy reserve (618) is a capacitor, super-capacitor, battery, orother device, that supplies a suitable supply of energy sufficient toenable the transfer of the contents of DRAM (616) to a stable storagemedium in the case of power loss. The flash memory (616) may beimplemented as multiple flash dies (622), which may be referred to aspackages of flash dies (622) or an array of flash dies (622). It shouldbe appreciated that the flash dies (622) could be packaged in any numberof ways, with a single die per package, multiple dies per package (i.e.multichip packages), in hybrid packages, as bare dies on a printedcircuit board or other substrate, as encapsulated dies, etc. In theembodiment shown, the non-volatile solid state storage (418) has acontroller (612) or other processor, and an I/O port (610) coupled tothe controller (612). The I/O (610) port may be coupled to the CPU (416)and/or the network interface controller (602) of the flash storage node(412). A flash I/O (620) port may be coupled to the flash dies (622),and a DMA (614) unit may be coupled to the controller (612), the DRAM(616), and the flash dies (622). In the embodiment shown, the I/O (610)port, controller (612), DMA unit (614), and flash I/O (620) port may beimplemented on a programmable logic device (PLD) (608), e.g., an FPGA.In this embodiment, each flash die (622) has pages, organized as sixteenkB (kilobyte) pages (624) and a register (626) through which data can bewritten to or read from the flash die (622). In further embodiments,other types of solid-state memory are used in place of, or in additionto flash memory illustrated within flash die (622).

Storage clusters, in various embodiments as disclosed herein, can becontrasted with storage arrays in general. The storage nodes (412) maybe part of a collection that creates the storage cluster. Each storagenode (412) may own a slice of data and computing required to provide thedata. Multiple storage nodes (412) can cooperate to store and retrievethe data. Storage memory or storage devices, as used in storage arraysin general, may be less involved with processing and manipulating thedata. Storage memory or storage devices in a storage array may receivecommands to read, write, or erase data. The storage memory or storagedevices in a storage array may not be aware of a larger system in whichthey are embedded, or what the data means. Storage memory or storagedevices in storage arrays can include various types of storage memory,such as RAM, solid state drives, hard disk drives, etc. The non-volatilesolid state storage (418) units described herein may have multipleinterfaces active simultaneously and serving multiple purposes. In someembodiments, some of the functionality of a storage node (412) isshifted into a non-volatile solid state storage (418) unit, transformingthe non-volatile solid state storage (418) unit into a combination ofnon-volatile solid state storage (418) unit and storage node (412).Placing computing (relative to storage data) into the non-volatile solidstate storage (418) unit places this computing closer to the dataitself. The various system embodiments have a hierarchy of storage nodelayers with different capabilities. By contrast, in a storage array, acontroller may own and know everything about all of the data that thecontroller manages in a shelf or storage devices. In a storage cluster,as described herein, multiple controllers in multiple non-volatile solidstate storage (418) units and/or storage nodes (412) may cooperate invarious ways (e.g., for erasure coding, data sharding, metadatacommunication and redundancy, storage capacity expansion or contraction,data recovery, and so on).

FIG. 7 illustrates a storage server environment, which may utilizeembodiments of the storage nodes and storage units according to someembodiments of the present disclosure. Each storage unit (752) depictedin FIG. 7 can include a processor (e.g., such as controller (612 in FIG.7), an FPGA, RAM (712), flash memory (706), and NVRAM (704) on a PCIeboard in a chassis. The storage unit (752) may be implemented as asingle board containing storage, and may be the largest tolerablefailure domain inside the chassis. In some embodiments, up to twostorage units (752) may fail and the device will continue with no dataloss.

The physical storage may be divided into named regions based onapplication usage in some embodiments. The NVRAM (704) may be acontiguous block of reserved memory in the storage unit (752) DRAM thatis backed by NAND flash. The NVRAM (704) may be logically divided intomultiple memory regions written for two as spool (e.g., spool_region).Space within the NVRAM (752) spools may be managed by each authorityindependently. Each device can provide an amount of storage space toeach authority. That authority can further manage lifetimes andallocations within that space. Examples of a spool include distributedtransactions or notions. When the primary power to a storage unit (752)fails, onboard super-capacitors can provide a short duration of powerhold up. During this holdup interval, the contents of the NVRAM (704)may be flushed to flash memory (706). On the next power-on, the contentsof the NVRAM (704) may be recovered from the flash memory (706).

As for the storage unit controller, the responsibility of the logical“controller” may be distributed across each of the blades containingauthorities. This distribution of logical control is shown in FIG. 7 asa host controller (702), a mid-tier controller (708), and one or morestorage unit controller (710). Management of the control plane and thestorage plane are treated independently, although parts may bephysically co-located on the same blade. Each authority can effectivelyserve as an independent controller. Each authority can provide its owndata and metadata structures, its own background workers, and maintainsits own lifecycle.

FIG. 8 illustrates a blade (802) hardware block diagram according tosome embodiments of the present disclosure. The example depicted in FIG.8 includes a control plane (804), a compute plane (806), a storage plane(808), and authorities (810) interacting with underlying physicalresources, using embodiments of the storage nodes, non-volatile solidstate storage, storage units, or any combination thereof. The controlplane (804) may be partitioned into a number of authorities (810) whichcan use the compute resources in the compute plane (806) to run on anyof the blades (802). The storage plane (808) may be partitioned into aset of devices, each of which provides access to flash (812) and NVRAM(814) resources.

In the compute plane (806) and storage planes (808) of FIG. 8, theauthorities (810) may interact with the underlying physical resources(i.e., devices). From the point of view of an authority (810), itsresources may be striped over multiple the physical devices. From thepoint of view of a device, it provides resources to multiple authorities(810), irrespective of where the authorities happen to run. In order tocommunicate and represent the ownership of an authority (810), includingthe right to record persistent changes on behalf of that authority(810), the authority (810) may provide some evidence of authorityownership that can be independently verifiable. A token, for example,may be employed for this purpose and function in one embodiment.

Each authority (810) may have allocated or have been allocated one ormore partitions (816) of storage memory in the storage units, e.g.partitions (816) in flash memory (812) and NVRAM (814). Each authority(810) may use those allocated partitions (816) that belong to it, forwriting or reading user data. Authorities can be associated withdiffering amounts of physical storage of the system. For example, oneauthority (810) could have a larger number of partitions (816) or largersized partitions (816) in one or more storage units than one or moreother authority (810).

Readers will appreciate that the storage systems and the components thatare contained in such storage systems, as described in the presentdisclosure, are included for explanatory purposes and do not representlimitations as to the types of systems that may be configured foron-demand content filtering of snapshots. In fact, storage systemsconfigured for dynamically adjusting an amount of log data generated maybe embodied in many other ways and may include fewer, additional, ordifferent components. For example, storage within storage systemsconfigured for dynamically adjusting an amount of log data generated maybe embodied as block storage where data is stored in blocks, and eachblock essentially acts as an individual hard drive. Alternatively,storage within storage systems configured for dynamically adjusting anamount of log data generated may be embodied as object storage, wheredata is managed as objects. Each object may include the data itself, avariable amount of metadata, and a globally unique identifier, whereobject storage can be implemented at multiple levels (e.g., devicelevel, system level, interface level). In addition, storage withinstorage systems configured for dynamically adjusting an amount of logdata generated may be embodied as file storage in which data is storedin a hierarchical structure. Such data may be saved in files andfolders, and presented to both the system storing it and the systemretrieving it in the same format. Such data may be accessed using theNetwork File System (‘NFS’) protocol for Unix or Linux, Server MessageBlock (‘SMB’) protocol for Microsoft Windows, or in some other manner.

For further explanation, FIG. 9 sets forth a flow chart illustrating anexample method of dynamically adjusting an amount of log data generatedfor a storage system (902) that includes a plurality of storage devices(920, 922, 924) according to some embodiments of the present disclosure.Although depicted in less detail, the storage system (902) depicted inFIG. 9 may be similar to the storage systems described above withreference to FIGS. 1-8. The storage system depicted in FIG. 9 caninclude a plurality of components (914, 916, 918). Each component (914,916, 918) may be embodied, for example, as one or more software modules,as one or more hardware modules, as a combination of one or moresoftware modules and one or more hardware modules, or as some otherlogical or physical entity in the storage system (902).

Readers will appreciate that log data may be generated for the storagesystem (902). Such log data may include information describing actionstaken by one or more components (914, 916, 918) in the storage system(902), the state of one or more components (914, 916, 918) in thestorage system (902) at various points in time, errors encountered byone or more components (914, 916, 918) in the storage system (902), orother information. Such log data may be analyzed, for example, by acloud-based management module or by some other management module toevaluate the operation of the storage system (902), to detect thepotential occurrence of some problem within the storage system (902), torecommend configuration settings or changes to the storage system (902),or for a variety of different reasons. Readers will appreciate, however,that in order for a cloud-based management module to evaluate such logdata, significant network resources may be consumed to send log data tothe cloud-based management module and significant processing resourcesmay be consumed to support the cloud-based management module's analysisof log data, even if the storage system (902) is healthy and operatingas expected.

The example method depicted in FIG. 9 can include setting (904), for acomponent (914, 916, 918) within the storage array, a logging level fora component (914, 916, 918). The logging level for a particularcomponent (914, 916, 918) can specify the extent to which log datashould be generated for particular component (914, 916, 918). Thelogging level for a particular component (914, 916, 918) may beembodied, for example, as a numerical value selected from a range ofpossible values that form a priority scale. For example, a value of ‘10’may indicate that generating log data for a particular component is ahighest priority, a value of ‘1’ indicates that that generating log datafor a particular component is a lowest priority, and the interveningvalues represent priority levels that increase as the numerical valuesincrease. In such an example, and in order to limit the amount ofnetwork resources that will be consumed to send log data to acloud-based management module and to limit the amount of processingresources consumed to support the cloud-based management module'sanalysis of log data, log data may only be generated for components witha logging level above a particular threshold (e.g., log data may only begenerated for components with a logging level of 7 or above). Setting(904) a logging level for a component (914, 916, 918) may be carriedout, for example, by applying a predetermined configuration when thestorage system (902) boots, by applying a predetermined configurationwhen the particular component (914, 916, 918) boots or is otherwiseadded to the storage system (902), by issuing a request or command tothe storage system (902) to set the logging level for one or morecomponents (914, 916, 918), or in other ways.

The example method depicted in FIG. 9 can also include determining(906), in dependence upon one or more measured operating characteristicsof the storage system (902), whether the logging level for a component(914, 916, 918) should be changed. In the example method depicted inFIG. 9, the one or more measured operating characteristics of thestorage system (902) can include quantifiable metrics that describe theoperation of the storage system (902). The one or more measuredoperating characteristics of the storage system (902) can include, forexample, information describing the number of errors experienced by aparticular component (914, 916, 918), information describing whether aparticular component (914, 916, 918) has experienced an error within apredetermined period of time, or other information describing the extentto which one or more components (914, 916, 918) are encountering errors.In addition to error-related information, the one or more measuredoperating characteristics of the storage system (902) may includeperformance-related information for one or more components (914, 916,918). Such performance-related information for one or more components(914, 916, 918) may include, for example, the number of requestsserviced during a predetermined period of time, the amount of datatransferred during a predetermined period of time, the average responsetime taken to service a request, an average amount of memory consumedduring a predetermined period of time, or many other types ofperformance-related information. In addition to error-relatedinformation and performance-related information, the one or moremeasured operating characteristics of the storage system (902) mayinclude state-related information for one or more components (914, 916,918). Such state-related information for one or more components (914,916, 918) may include, for example, information describing whether thecomponent is powered on, information describing whether the component isactively executing, information describing one or more protocols used bya particular component, information describing a firmware versionexecuting on a particular component, information describing the releaseversion of a particular component, or many other types of state-relatedinformation.

In the example method depicted in FIG. 9, determining (906) whether thelogging level for a component (914, 916, 918) should be changed independence upon one or more measured operating characteristics of thestorage system (902) may be carried out, for example, by examining theone or more measured operating characteristics of the storage system(902) to determine whether a particular component (914, 916, 918) hasexperienced a predetermined number of errors within a predeterminedperiod of time. Readers will appreciate that if a particular component(914, 916, 918) has experienced a predetermined number of errors withina predetermined period of time, the logging level for the particularcomponent (914, 916, 918) may be increased or otherwise changed suchthat log data is more likely to be generated for the particularcomponent (914, 916, 918). Readers will further appreciate that somecomponents may be more error-tolerant than other components and that, assuch, the error threshold for one component may be higher than the errorthreshold for another component. For example, a first component may bepermitted to experience 100 errors/minute without resulting in anincrease to its error logging level while a second component may haveits error logging level changed to the highest available level inresponse to experiencing a single error.

Determining (906) whether the logging level for a component (914, 916,918) should be changed in dependence upon one or more measured operatingcharacteristics may also be carried out, for example, by comparing theone or more measured operating characteristics of the storage system(902) to one or more fingerprints of known system behavior. Suchfingerprints may include information that describes the error-relatedcharacteristics, performance-related characteristics, state-relatedcharacteristics, or any combination of such characteristics that areexhibited by storage systems that are exhibiting a particular behavior.For example, a first fingerprint may include information indicating thatwhen a particular software component on the storage system has aparticular version number, a network adapter on the storage system isreceiving more than a predetermined number of requests per unit of time,and the storage devices have less than a predetermined amount ofavailable capacity, the storage system tends to exhibit the behavior ofhaving an average I/O latency that is above an acceptable threshold. Insuch an example, if it is determined that the one or more measuredoperating characteristics are in alignment with the first fingerprint,the storage system (902) may determine that the logging level for one ormore components (914, 916, 918) should be changed by increasing orotherwise changing the logging level for a particular component (914,916, 918) such that log data is more likely to be generated for theparticular component (914, 916, 918), as being in alignment with thefirst fingerprint tends to correlate with storage systems performing atundesirable levels. When the storage system is performing at undesirablelevels, additional logging data may be useful as a diagnostic input.

As an additional example, a second fingerprint may include informationindicating that when firmware on the storage devices in the storagesystem has a particular version number, a network adapter is sending andreceiving data using a particular protocol, and a particular softwarecomponent (e.g., a garbage collection process), the storage system tendsto exhibit the behavior of having an average I/O latency that is belowan acceptable threshold. In such an example, if it is determined thatthe one or more measured operating characteristics are in alignment withthe second fingerprint, the storage system (902) may determine that thelogging level for one or more components (914, 916, 918) should bechanged by decreasing or otherwise changing the logging level for aparticular component (914, 916, 918) such that log data is less likelyto be generated for the particular component (914, 916, 918), as beingin alignment with the second fingerprint tends to correlate with storagesystems performing at acceptable levels. When the storage system isperforming at acceptable levels, it may be undesirable to dedicatesignificant resources to performing diagnostic operations on a storagesystem that appears to be relatively healthy.

Readers will appreciate that such fingerprints may be developed, forexample, by processing log data and other forms of telemetry data frommany storage systems to identify patterns exhibited by storage systemsthat are exhibiting (or are predicted to exhibit) some known behavior.In the example method depicted in FIG. 9, comparing the one or moremeasured operating characteristics of the storage system (902) to one ormore fingerprints may be carried out in real-time or, as onealternative, by a module on a cloud-based services provider comparinglog data or other forms of telemetry data from the storage system (902)to a catalog of fingerprints.

Although the preceding paragraphs describes embodiments wheredetermining (906) whether the logging level for a component (914, 916,918) should be changed in dependence upon one or more measured operatingcharacteristics of the storage system (902) results in increasing orotherwise changing the logging level for a particular component (914,916, 918) such that log data is more likely to be generated for theparticular component (914, 916, 918), the storage system (902) may alsodetermine (906) that the logging level for a component (914, 916, 918)should be decreased or otherwise changed such that log data is lesslikely to be generated for the particular component (914, 916, 918).Decreasing the logging level or otherwise changing the logging levelsuch that log data is less likely to be generated for the particularcomponent (914, 916, 918) may occur over time, for example, bydecreasing the logging level by one unit after the expiration of apredetermined period of time without experiencing an error.Alternatively, decreasing the logging level or otherwise changing thelogging level such that log data is less likely to be generated for theparticular component (914, 916, 918) may occur over instantaneously, forexample, by decreasing the logging level in response to the occurrenceof some event such as the component falling out of alignment with afingerprint. Increasing the logging level or otherwise changing thelogging level such that log data is more likely to be generated for theparticular component (914, 916, 918) may also occur over time orinstantaneously.

The example method depicted in FIG. 9 can also include, responsive toaffirmatively (908) determining that the logging level for the component(914, 916, 918) should be changed, changing (912) the logging levelassociated with the component (914, 916, 918). Changing (912) thelogging level associated with the component (914, 916, 918) may becarried out, for example, by decreasing the logging level by apredetermined amount, by increasing the logging level a predeterminedamount, by increasing the logging level to the highest available value,by decreasing the logging level to the lowest available value, and inother ways. In such an example, changing (912) the logging levelassociated with the component may be carried out by issuing a request orcommand to the storage system (902) to set the logging level for one ormore components (914, 916, 918), in response to the storage system (902)receiving a request or command to change the logging level for one ormore components (914, 916, 918), or in other ways. Readers willappreciate that if the storage system (902) determines that the logginglevel for the component (914, 916, 918) should not (910) be changed, thestorage system (902) may continue be monitored.

For further explanation, FIG. 10 sets forth a flow chart illustrating anadditional example method of dynamically adjusting an amount of log datagenerated for a storage system (902) that includes a plurality ofstorage devices (920, 922, 924) according to some embodiments of thepresent disclosure. The example method depicted in FIG. 10 is similar tothe example method depicted in FIG. 9, as the example method depicted inFIG. 10 also includes setting (904), for a component (914, 916, 918)within the storage array, a logging level for a component (914, 916,918), determining (906), in dependence upon one or more measuredoperating characteristics of the storage system (902), whether thelogging level for a component (914, 916, 918) should be changed, andresponsive to affirmatively (908) determining that the logging level forthe component (914, 916, 918) should be changed, changing (912) thelogging level associated with the component (914, 916, 918).

In the example method depicted in FIG. 10, determining (906) whether thelogging level for a component (914, 916, 918) should be changed caninclude detecting (1002) that an error has been encountered by one ormore components (914, 916, 918) in the storage system (902). Detecting(1002) that an error has been encountered by one or more components(914, 916, 918) in the storage system (902) may be carried out, forexample, by examining an error log, by examining log data that includesan identification of errors encountered by components within the storagesystem, by receiving a message or other form of notification from acomponent that has experienced an error, or in some other way. Readerswill appreciate that because an error has been encountered by one ormore components (914, 916, 918) in the storage system (902), it may bedesirable to have the storage system (902) generate more robust logssuch that one or more components (914, 916, 918) in the storage system(902) may be closely monitored.

In the example method depicted in FIG. 10, determining (906) whether thelogging level for a component (914, 916, 918) should be changed can alsoinclude detecting (1004) that one or more operating characteristics ofthe storage system (902) matches a predetermined operatingcharacteristic fingerprint. A predetermined operating characteristicfingerprint may include information that describes the error-relatedcharacteristics, performance-related characteristics, state-relatedcharacteristics, or any combination of such characteristics that areexhibited by storage systems that are exhibiting a particular behavior.For example, a first predetermined operating characteristic fingerprintmay include information indicating that when a particular softwarecomponent on the storage system has a particular version number, anetwork adapter on the storage system is receiving more than apredetermined number of requests per unit of time, and the storagedevices have less than a predetermined amount of available capacity, thestorage system tends to exhibit the behavior of having an average I/Olatency that is above an acceptable threshold. In such an example, if itis determined that operating characteristics of the storage system (902)matches such a predetermined operating characteristic fingerprint, thestorage system (902) may determine that the logging level for one ormore components (914, 916, 918) should be changed by increasing orotherwise changing the logging level for a particular component (914,916, 918) such that log data is more likely to be generated for theparticular component (914, 916, 918), as being in alignment with thefirst predetermined operating characteristic fingerprint tends tocorrelate with storage systems performing at undesirable levels. Whenthe storage system is performing at undesirable levels, additionallogging data may be useful as a diagnostic input.

As an additional example, a second predetermined operatingcharacteristic fingerprint may include information indicating that whenfirmware on the storage devices in the storage system has a particularversion number, a network adapter is sending and receiving data using aparticular protocol, and a particular software component (e.g., agarbage collection process), the storage system tends to exhibit thebehavior of having an average I/O latency that is below an acceptablethreshold. In such an example, if it is determined that operatingcharacteristics of the storage system (902) matches such a predeterminedoperating characteristic fingerprint, the storage system (902) maydetermine that the logging level for one or more components (914, 916,918) should be changed by decreasing or otherwise changing the logginglevel for a particular component (914, 916, 918) such that log data isless likely to be generated for the particular component (914, 916,918), as being in alignment with the second predetermined operatingcharacteristic fingerprint tends to correlate with storage systemsperforming at acceptable levels. When the storage system is performingat acceptable levels, it may be undesirable to dedicate significantresources to performing diagnostic operations on a storage system thatappears to be relatively healthy. Readers will appreciate that suchpredetermined operating characteristic fingerprint may be developed, forexample, by processing log data and other forms of telemetry data frommany storage systems to identify patterns exhibited by storage systemsthat are exhibiting (or are predicted to exhibit) some known behavior.

In the example method depicted in FIG. 10, detecting (1004) that one ormore operating characteristics of the storage system (902) matches apredetermined operating characteristic fingerprint can include comparing(1006) log data generated by the storage system (902) to one or moreoperating characteristic fingerprints. Comparing (1006) log datagenerated by the storage system (902) to one or more operatingcharacteristic fingerprints may be carried out, for example, by anentity such as a controller as the log data is being generated or, in analternative embodiment, by an entity such as a cloud-based managementmodule, a remote array-services provider, or other entity. As such,comparing (1006) log data generated by the storage system (902) to oneor more operating characteristic fingerprints may be part of a largereffort to analyze the content of log data for the purpose of monitoringand evaluating the operation of the storage system (902).

In the example method depicted in FIG. 10, determining (906) whether thelogging level for a component (914, 916, 918) should be changed can alsoinclude evaluating (1008) results from a health check of the storagesystem (902). A health check of the storage system (902) may beperformed by one or more modules that are executing on the storage arraycontroller or on some other device. Such modules may include computerprogram instructions that, when executed, perform a scan of the storagesystem (902) to determine whether various components of the storagesystem (902), and the storage system (902) generally, are operatingwithin specified parameters. Such a health check may be performedperiodically and may provide ongoing analysis of the health of thestorage system (902) and the components contained therein. In such anexample, if the results from a health check of the storage system (902)indicate that one or more components are not operating as expected, thelogging level for one or more components (914, 916, 918) may be changedby increasing or otherwise changing the logging level for a particularcomponent (914, 916, 918) such that log data is more likely to begenerated for the particular component (914, 916, 918). Alternatively,if the results from a health check of the storage system (902) indicatethat one or more components are operating as expected, the logging levelfor such components (914, 916, 918) may be changed by decreasing orotherwise changing the logging level for a particular component (914,916, 918) such that log data is less likely to be generated for thecomponents (914, 916, 918). Evaluating (1008) results from a healthcheck of the storage system (902) may be carried out, for example, by anentity such as a controller as the results from the health check arebeing generated or, in an alternative embodiment, by an entity such as acloud-based management module, a remote array-services provider, orother entity. As such, evaluating (1008) results from a health check maybe part of a larger effort to monitor and evaluate the operation of thestorage system (902).

In the example method depicted in FIG. 10, determining (906) whether thelogging level for a component (914, 916, 918) should be changed can alsoinclude detecting (1010) that a predetermined amount of time has lapsedsince an error has been encountered by one or more components (914, 916,918) in the storage system (902). Detecting (1010) that a predeterminedamount of time has lapsed since an error has been encountered by one ormore components (914, 916, 918) in the storage system (902) may becarried out, for example, through the use of one or more timers thatreset when an error is encountered by one or more particular components(914, 916, 918), by periodically comparing a time stamp that isassociated with the last error that was encountered by one or moreparticular components (914, 916, 918) to a current clock time, and inother ways. In some embodiments, when it is detected (1010) that apredetermined amount of time has lapsed since an error has beenencountered by one or more particular components (914, 916, 918), thelogging level associated with the one or more particular components(914, 916, 918) may be decreased or otherwise changed such that log datais less likely to be generated for the one or more particular components(914, 916, 918). In such a way, a decay schedule may be set up such thatas components return to health and cease encountering errors, the amountof log data that is generated for the one or more particular components(914, 916, 918) decreases.

For further explanation, FIG. 11 sets forth a flow chart illustrating anadditional example method of dynamically adjusting an amount of log datagenerated for a storage system (902) that includes a plurality ofstorage devices (920, 922, 924) according to some embodiments of thepresent disclosure. The example method depicted in FIG. 11 is carriedout, at least in part, by a storage system services provider (1102). Thestorage system services provider (1102) may be embodied, for example, asone or more servers or other computing devices that are not part of thestorage system (902), as a collection of cloud resources that are notpart of the storage system (902), or as some other remote system thatprovides services to a storage system (902).

The example method depicted in FIG. 11 includes receiving (1104) logdata (1100) generated by the storage system (902). In the example methoddepicted in FIG. 11, the storage system services provider (1102) mayreceive (1104) log data (1100) generated by the storage system (902),for example, via one or more message received from the storage system(902), by polling the storage system (902) for log data (1100), or inother ways. In such an example, the storage system services provider(1102) and the storage system (902) may be coupled for datacommunications via one or more data communications networks, via adedicated data communications link, or in some other way. In someembodiments, the log data (1100) may be encrypted using data encryptionkeys, communication links may be secure, or other security measures maybe taken to protect the log data (1100).

The example method depicted in FIG. 11 also includes determining (1106),in dependence upon one or more measured operating characteristics of thestorage system (902), whether the logging level for a component (914,916, 918) should be changed. In the example method depicted in FIG. 11,the one or more measured operating characteristics of the storage system(902) can include quantifiable metrics that describe the operation ofthe storage system (902). The one or more measured operatingcharacteristics of the storage system (902) can include, for example,information describing the number of errors experienced by a particularcomponent (914, 916, 918), information describing whether a particularcomponent (914, 916, 918) has experienced an error within apredetermined period of time, or other information describing the extentto which one or more components (914, 916, 918) are encountering errors.In addition to error-related information, the one or more measuredoperating characteristics of the storage system (902) may includeperformance-related information for one or more components (914, 916,918). Such performance-related information for one or more components(914, 916, 918) may include, for example, the number of requestsserviced during a predetermined period of time, the amount of datatransferred during a predetermined period of time, the average responsetime taken to service a request, an average amount of memory consumedduring a predetermined period of time, or many other types ofperformance-related information. In addition to error-relatedinformation and performance-related information, the one or moremeasured operating characteristics of the storage system (902) mayinclude state-related information for one or more components (914, 916,918). Such state-related information for one or more components (914,916, 918) may include, for example, information describing whether thecomponent is powered on, information describing whether the component isactively executing, information describing one or more protocols used bya particular component, information describing a firmware versionexecuting on a particular component, information describing the releaseversion of a particular component, or many other types of state-relatedinformation.

In the example method depicted in FIG. 11, determining (1106) whetherthe logging level for a component (914, 916, 918) should be changed independence upon one or more measured operating characteristics of thestorage system (902) may be carried out, for example, by examining theone or more measured operating characteristics of the storage system(902) to determine whether a particular component (914, 916, 918) hasexperienced a predetermined number of errors within a predeterminedperiod of time. Readers will appreciate that if a particular component(914, 916, 918) has experienced a predetermined number of errors withina predetermined period of time, the logging level for the particularcomponent (914, 916, 918) may be increased or otherwise changed suchthat log data is more likely to be generated for the particularcomponent (914, 916, 918). Readers will further appreciate that somecomponents may be more error-tolerant than other components and that, assuch, the error threshold for one component may be higher than the errorthreshold for another component. For example, a first component may bepermitted to experience 100 errors/minute without resulting in anincrease to its error logging level while a second component may haveits error logging level changed to the highest available level inresponse to experiencing a single error.

Determining (1106) whether the logging level for a component (914, 916,918) should be changed in dependence upon one or more measured operatingcharacteristics may also be carried out, for example, by comparing theone or more measured operating characteristics of the storage system(902) to one or more fingerprints of known system behavior. Suchfingerprints may include information that describes the error-relatedcharacteristics, performance-related characteristics, state-relatedcharacteristics, or any combination of such characteristics that areexhibited by storage systems that are exhibiting a particular behavior.For example, a first fingerprint may include information indicating thatwhen a particular software component on the storage system has aparticular version number, a network adapter on the storage system isreceiving more than a predetermined number of requests per unit of time,and the storage devices have less than a predetermined amount ofavailable capacity, the storage system tends to exhibit the behavior ofhaving an average I/O latency that is above an acceptable threshold. Insuch an example, if it is determined that the one or more measuredoperating characteristics are in alignment with the first fingerprint,the storage system (902) may determine that the logging level for one ormore components (914, 916, 918) should be changed by increasing orotherwise changing the logging level for a particular component (914,916, 918) such that log data is more likely to be generated for theparticular component (914, 916, 918), as being in alignment with thefirst fingerprint tends to correlate with storage systems performing atundesirable levels. When the storage system is performing at undesirablelevels, additional logging data may be useful as a diagnostic input.

As an additional example, a second fingerprint may include informationindicating that when firmware on the storage devices in the storagesystem has a particular version number, a network adapter is sending andreceiving data using a particular protocol, and a particular softwarecomponent (e.g., a garbage collection process), the storage system tendsto exhibit the behavior of having an average I/O latency that is belowan acceptable threshold. In such an example, if it is determined thatthe one or more measured operating characteristics are in alignment withthe second fingerprint, the storage system (902) may determine that thelogging level for one or more components (914, 916, 918) should bechanged by decreasing or otherwise changing the logging level for aparticular component (914, 916, 918) such that log data is less likelyto be generated for the particular component (914, 916, 918), as beingin alignment with the second fingerprint tends to correlate with storagesystems performing at acceptable levels. When the storage system isperforming at acceptable levels, it may be undesirable to dedicatesignificant resources to performing diagnostic operations on a storagesystem that appears to be relatively healthy.

Readers will appreciate that such fingerprints may be developed, forexample, by processing log data and other forms of telemetry data frommany storage systems to identify patterns exhibited by storage systemsthat are exhibiting (or are predicted to exhibit) some known behavior.In the example method depicted in FIG. 11, comparing the one or moremeasured operating characteristics of the storage system (902) to one ormore fingerprints may be carried out in real-time or, as onealternative, by a module on a cloud-based services provider comparinglog data or other forms of telemetry data from the storage system (902)to a catalog of fingerprints.

Although the preceding paragraphs describes embodiments wheredetermining (1106) whether the logging level for a component (914, 916,918) should be changed in dependence upon one or more measured operatingcharacteristics of the storage system (902) results in increasing orotherwise changing the logging level for a particular component (914,916, 918) such that log data is more likely to be generated for theparticular component (914, 916, 918), the storage system (902) may alsodetermine (1106) that the logging level for a component (914, 916, 918)should be decreased or otherwise changed such that log data is lesslikely to be generated for the particular component (914, 916, 918).Decreasing the logging level or otherwise changing the logging levelsuch that log data is less likely to be generated for the particularcomponent (914, 916, 918) may occur over time, for example, bydecreasing the logging level by one unit after the expiration of apredetermined period of time without experiencing an error.Alternatively, decreasing the logging level or otherwise changing thelogging level such that log data is less likely to be generated for theparticular component (914, 916, 918) may occur over instantaneously, forexample, by decreasing the logging level in response to the occurrenceof some event such as the component falling out of alignment with afingerprint. Increasing the logging level or otherwise changing thelogging level such that log data is more likely to be generated for theparticular component (914, 916, 918) may also occur over time orinstantaneously.

In the example method depicted in FIG. 11, determining (1106) whetherthe logging level for a component (914, 916, 918) should be changed caninclude detecting (1108) that an error has been encountered by one ormore components (914, 916, 918) in the storage system (902). Detecting(1108) that an error has been encountered by one or more components(914, 916, 918) in the storage system (902) may be carried out, forexample, by examining an error log, by examining log data that includesan identification of errors encountered by components within the storagesystem, by receiving a message or other form of notification from acomponent that has experienced an error, or in some other way. Readerswill appreciate that because an error has been encountered by one ormore components (914, 916, 918) in the storage system (902), it may bedesirable to have the storage system (902) generate more robust logssuch that one or more components (914, 916, 918) in the storage system(902) may be closely monitored.

In the example method depicted in FIG. 11, determining (1106) whetherthe logging level for a component (914, 916, 918) should be changed canalso include detecting (1110) that one or more operating characteristicsof the storage system (902) matches a predetermined operatingcharacteristic fingerprint. A predetermined operating characteristicfingerprint may include information that describes the error-relatedcharacteristics, performance-related characteristics, state-relatedcharacteristics, or any combination of such characteristics that areexhibited by storage systems that are exhibiting a particular behavior.For example, a first predetermined operating characteristic fingerprintmay include information indicating that when a particular softwarecomponent on the storage system has a particular version number, anetwork adapter on the storage system is receiving more than apredetermined number of requests per unit of time, and the storagedevices have less than a predetermined amount of available capacity, thestorage system tends to exhibit the behavior of having an average I/Olatency that is above an acceptable threshold. In such an example, if itis determined that operating characteristics of the storage system (902)matches such a predetermined operating characteristic fingerprint, thestorage system services provider (1102) may determine that the logginglevel for one or more components (914, 916, 918) should be changed byincreasing or otherwise changing the logging level for a particularcomponent (914, 916, 918) such that log data is more likely to begenerated for the particular component (914, 916, 918), as being inalignment with the first predetermined operating characteristicfingerprint tends to correlate with storage systems performing atundesirable levels. When the storage system is performing at undesirablelevels, additional logging data may be useful as a diagnostic input.

As an additional example, a second predetermined operatingcharacteristic fingerprint may include information indicating that whenfirmware on the storage devices in the storage system has a particularversion number, a network adapter is sending and receiving data using aparticular protocol, and a particular software component (e.g., agarbage collection process), the storage system tends to exhibit thebehavior of having an average I/O latency that is below an acceptablethreshold. In such an example, if it is determined that operatingcharacteristics of the storage system (902) matches such a predeterminedoperating characteristic fingerprint, the storage system servicesprovider (1102) may determine that the logging level for one or morecomponents (914, 916, 918) should be changed by decreasing or otherwisechanging the logging level for a particular component (914, 916, 918)such that log data is less likely to be generated for the particularcomponent (914, 916, 918), as being in alignment with the secondpredetermined operating characteristic fingerprint tends to correlatewith storage systems performing at acceptable levels. When the storagesystem is performing at acceptable levels, it may be undesirable todedicate significant resources to performing diagnostic operations on astorage system that appears to be relatively healthy. Readers willappreciate that such predetermined operating characteristic fingerprintmay be developed, for example, by processing log data and other forms oftelemetry data from many storage systems to identify patterns exhibitedby storage systems that are exhibiting (or are predicted to exhibit)some known behavior.

In the example method depicted in FIG. 11, detecting (1110) that one ormore operating characteristics of the storage system (902) matches apredetermined operating characteristic fingerprint can include comparing(1112) log data generated by the storage system (902) to one or moreoperating characteristic fingerprints. Comparing (1112) log datagenerated by the storage system (902) to one or more operatingcharacteristic fingerprints may be carried out, for example, by anentity such as a controller as the log data is being generated or, in analternative embodiment, by an entity such as a cloud-based managementmodule, a remote array-services provider, or other entity. As such,comparing (1112) log data generated by the storage system (902) to oneor more operating characteristic fingerprints may be part of a largereffort to analyze the content of log data for the purpose of monitoringand evaluating the operation of the storage system (902).

In the example method depicted in FIG. 11, determining (1106) whetherthe logging level for a component (914, 916, 918) should be changed canalso include evaluating (1114) results from a health check of thestorage system (902). A health check of the storage system (902) may beperformed by one or more modules that are executing on the storage arraycontroller, by one or more modules that are executing on the storagesystem services provider (1102), or on some other device. Such modulesmay include computer program instructions that, when executed, perform ascan of the storage system (902) to determine whether various componentsof the storage system (902), and the storage system (902) generally, areoperating within specified parameters. Such a health check may beperformed periodically and may provide ongoing analysis of the health ofthe storage system (902) and the components contained therein. In suchan example, if the results from a health check of the storage system(902) indicate that one or more components are not operating asexpected, the logging level for one or more components (914, 916, 918)may be changed by increasing or otherwise changing the logging level fora particular component (914, 916, 918) such that log data is more likelyto be generated for the particular component (914, 916, 918).Alternatively, if the results from a health check of the storage system(902) indicate that one or more components are operating as expected,the logging level for such components (914, 916, 918) may be changed bydecreasing or otherwise changing the logging level for a particularcomponent (914, 916, 918) such that log data is less likely to begenerated for the components (914, 916, 918). Evaluating (1114) resultsfrom a health check of the storage system (902) may be carried out, forexample, by as part of a larger effort to monitor and evaluate theoperation of the storage system (902).

In the example method depicted in FIG. 11, determining (1106) whetherthe logging level for a component (914, 916, 918) should be changed canalso include detecting (1116) that a predetermined amount of time haslapsed since an error has been encountered by one or more components(914, 916, 918) in the storage system (902). Detecting (1116) that apredetermined amount of time has lapsed since an error has beenencountered by one or more components (914, 916, 918) in the storagesystem (902) may be carried out, for example, through the use of one ormore timers that reset when an error is encountered by one or moreparticular components (914, 916, 918), by periodically comparing a timestamp that is associated with the last error that was encountered by oneor more particular components (914, 916, 918) to a current clock time,and in other ways. In some embodiments, when it is detected (1116) thata predetermined amount of time has lapsed since an error has beenencountered by one or more particular components (914, 916, 918), thelogging level associated with the one or more particular components(914, 916, 918) may be decreased or otherwise changed such that log datais less likely to be generated for the one or more particular components(914, 916, 918). In such a way, a decay schedule may be set up such thatas components return to health and cease encountering errors, the amountof log data that is generated for the one or more particular components(914, 916, 918) decreases.

The example method depicted in FIG. 11 also includes, responsive toaffirmatively (1118) determining that the logging level for thecomponent (914, 916, 918) should be changed, changing (1122) the logginglevel associated with the component (914, 916, 918). Changing (1122) thelogging level associated with the component (914, 916, 918) may becarried out, for example, by decreasing the logging level by apredetermined amount, by increasing the logging level a predeterminedamount, by increasing the logging level to the highest available value,by decreasing the logging level to the lowest available value, and inother ways. In such an example, changing (1122) the logging levelassociated with the component may be carried out by issuing a request orcommand to the storage system (902) to set the logging level for one ormore components (914, 916, 918), by the storage system services provider(1102) modifying the logging level for one or more components, or inother ways. Readers will appreciate that if the storage system (902)determines that the logging level for the component (914, 916, 918)should not (1120) be changed, the storage system (902) may continue bemonitored.

Readers will appreciate that although the example methods describedabove are depicted in a way where a series of steps occurs in aparticular order, no particular ordering of the steps is required unlessexplicitly stated. Example embodiments of the present disclosure aredescribed largely in the context of a fully functional computer systemfor dynamically adjusting an amount of log data generated for a storagesystem. Readers of skill in the art will recognize, however, that thepresent disclosure also may be embodied in a computer program productdisposed upon computer readable storage media for use with any suitabledata processing system. Such computer readable storage media may be anystorage medium for machine-readable information, including magneticmedia, optical media, or other suitable media. Examples of such mediainclude magnetic disks in hard drives or diskettes, compact disks foroptical drives, magnetic tape, and others as will occur to those ofskill in the art. Persons skilled in the art will immediately recognizethat any computer system having suitable programming means will becapable of executing the steps of the method of the disclosure asembodied in a computer program product. Persons skilled in the art willrecognize also that, although some of the example embodiments describedin this specification are oriented to software installed and executingon computer hardware, nevertheless, alternative embodiments implementedas firmware or as hardware are well within the scope of the presentdisclosure.

The present disclosure may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent disclosure.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present disclosure may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present disclosure.

Aspects of the present disclosure are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to some embodimentsof the disclosure. It will be understood that each block of theflowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present disclosure. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Readers will appreciate that the steps described herein may be carriedout in a variety ways and that no particular ordering is required. Itwill be further understood from the foregoing description thatmodifications and changes may be made in various embodiments of thepresent disclosure without departing from its true spirit. Thedescriptions in this specification are for purposes of illustration onlyand are not to be construed in a limiting sense. The scope of thepresent disclosure is limited only by the language of the followingclaims.

What is claimed is:
 1. A method of dynamically adjusting an amount oflog data generated for a storage system that includes a plurality ofstorage devices, the method comprising: setting, for a component withinthe storage system, a logging level for the component, the logging levelspecifying the extent to which log data should be generated for aparticular component; determining, in dependence upon one or moremeasured operating characteristics of the storage system, whether thelogging level for the component should be changed; and responsive todetermining that the logging level for the component should be changed,changing the logging level associated with the component.
 2. The methodof claim 1 wherein determining that the logging level for the componentshould be changed further comprises detecting that an error has beenencountered by one or more components in the storage system.
 3. Themethod of claim 1 wherein determining that the logging level for thecomponent should be changed further comprises detecting that one or moreoperating characteristics of the storage system matches a predeterminedoperating characteristic fingerprint.
 4. The method of claim 3 whereindetecting that one or more operating characteristics of the storagesystem matches a predetermined operating characteristic fingerprintfurther comprises comparing log data generated by the storage system toone or more operating characteristic fingerprints.
 5. The method ofclaim 1 wherein determining that the logging level for the componentshould be changed further comprises evaluating results from a healthcheck of the storage system.
 6. The method of claim 1 whereindetermining, in dependence upon one or more measured operatingcharacteristics of the storage system, that the logging level for thecomponent should be changed further comprises detecting that apredetermined amount of time has lapsed since an error has beenencountered by one or more components in the storage system.
 7. A methodof dynamically adjusting an amount of log data generated for a storagesystem that includes a plurality of storage devices, the methodcomprising: receiving log data from the storage system; determining, independence upon one or more measured operating characteristics of thestorage system, whether the logging level for a component should bechanged, the logging level specifying the extent to which log datashould be generated for a particular component; and responsive todetermining that the logging level for the component should be changed,changing the logging level associated with the component.
 8. The methodof claim 7 wherein determining that the logging level for the componentshould be changed further comprises detecting that an error has beenencountered by one or more components in the storage system.
 9. Themethod of claim 7 wherein determining that the logging level for thecomponent should be changed further comprises detecting that one or moreoperating characteristics of the storage system matches a predeterminedoperating characteristic fingerprint.
 10. The method of claim 9 whereindetecting that one or more operating characteristics of the storagesystem matches a predetermined operating characteristic fingerprintfurther comprises comparing log data generated by the storage system toone or more operating characteristic fingerprints.
 11. The method ofclaim 7 wherein determining that the logging level for the componentshould be changed further comprises evaluating results from a healthcheck of the storage system.
 12. The method of claim 7 whereindetermining, in dependence upon one or more measured operatingcharacteristics of the storage system, that the logging level for thecomponent should be changed further comprises detecting that apredetermined amount of time has lapsed since an error has beenencountered by one or more components in the storage system.
 13. Anapparatus for dynamically adjusting an amount of log data generated fora storage system that includes a plurality of storage devices, theapparatus comprising a computer processor, a computer memory operativelycoupled to the computer processor, the computer memory having disposedwithin it computer program instructions that, when executed by thecomputer processor, cause the apparatus to carry out the steps of:determining, in dependence upon one or more measured operatingcharacteristics of the storage system, whether a logging level for acomponent should be changed, the logging level specifying the extent towhich log data should be generated for a particular component; andresponsive to determining that the logging level for the componentshould be changed, changing the logging level associated with thecomponent
 14. The apparatus of claim 13 further comprising computerprogram instructions that, when executed by the computer processor,cause the apparatus to carry out the step of receiving log data from thestorage system.
 15. The apparatus of claim 13 further comprisingcomputer program instructions that, when executed by the computerprocessor, cause the apparatus to carry out the steps of setting, for acomponent within the storage system, a logging level for the component,the logging level specifying the extent to which log data should begenerated for a particular component.
 16. The apparatus of claim 13wherein determining that the logging level for the component should bechanged further comprises detecting that an error has been encounteredby one or more components in the storage system.
 17. The apparatus ofclaim 13 wherein determining that the logging level for the componentshould be changed further comprises detecting that one or more operatingcharacteristics of the storage system matches a predetermined operatingcharacteristic fingerprint.
 18. The apparatus of claim 17 whereindetecting that one or more operating characteristics of the storagesystem matches a predetermined operating characteristic fingerprintfurther comprises comparing log data generated by the storage system toone or more operating characteristic fingerprints.
 19. The apparatus ofclaim 13 wherein determining that the logging level for the componentshould be changed further comprises evaluating results from a healthcheck of the storage system.
 20. The apparatus of claim 13 determining,in dependence upon one or more measured operating characteristics of thestorage system, that the logging level for the component should bechanged further comprises detecting that a predetermined amount of timehas lapsed since an error has been encountered by one or more componentsin the storage system.